Proceeding for burning in piles the articles of nonglazed porcelain especially suitable for cooling use



i atented July 11, 1933 Unit's STATES PATEN oFFIcE GIOVANNI FUSGI-II, OF CASTELLI-TERAMO, AND MAURIZIO HORACE, OF BOLOGNA,

ITALY Y rnocnnnrne ron- BURNING m FILES rnnnnricnns or .nonenaznn PORCELAIN ESPECIALLY SUITABLE FOB,'COOLING USE No Drawing The present invention has for its object a special proceeding for burning articles of porcelain, W iereby a type of porcelain is obtained which may be more cheaply produced and is particularly resistant to heat.

It is known that one of the principal reasons of the high price of articles of porcelain is that the pieces to be burnt occupy a very large place in the furnace, as they must be placed in separated saggers in order to avoid being attached to one another during the burning at high temperatures, that is at temperatures at which vitrification takes place when the articles are burnt without glaze, at high temperatures, they can be burnt in piles without incurring the risk of remaining attached together if they be separated by means of a layer of a. nonadhesive substance. But such a layer remains at- 'tached to the surface of separation of the difierent articles, resulting in an uneven surface. nated, only in an imperfect manner by means of an expensive grinding operation.

This inconvenience is avoided, according to the present invention, by plunging the articles, raw or after preliminary baking at low temperatures (glow-burning) into a special anti-adhesive mixture, composed of refractory substances and organic glutinous substances, so that the said mixture remains adherent to the outer bottom of the articles, while their interior side on which the said bottoms are leaned is leftperfectly smooth. Solely by way of example, the composition of one of such anti-adhesive mixtures is:

Percent Alumina n 4O Burnt kaolin Dextrin 5 they are rendered suitable to be used I 50 without glaze, the anti-adhesive layer be- This uneven surface 'can' be elimi- 7 it is only possible to arrive Application filed October 9, 1930. Serial No. 487,630.

ing then taken'away only from the external side of the articles, Where some small vestige eventually remaining adherent does not cause a special trouble. hBeside the smaller cost of the articles 5 manufactured in such a way, they have also the'advantage of being more resistant to fire thanthe glazed porcelain.

In fact,,it is known that the kitchen porcelain for cooking use-must have as an essential characteristic a high resistance to sudden changes in temperature. This re sistance is determinated by the similarity of characteristics of the mass and the cover (glaze); that is to say, the more nearly alike the coeflicients of expansion and the moduli of elasticity of the two substances which formthe object of porcelain will be, the more certain will be the elimination of splits and ruptures in consequence of the 7 sudden changes in temperature.

'Butin practice it is impossible to find a mass and a cover (glaze) which in this respect are exactly alike, because in this case both substances ought naturally to have the same physico-chemical composition, which would cause the exclusion of the; one or of the other of the two constituting elements of the usual porcelain.

Besides, in process of time, the successive 0 changes of temperaturecause in the mass as well as in the glaze so'memodifications of structure, which, also if at first the coefficients of expansion and the moduli of elasticity had been p'ractically'identical, cause 35 their values to become different from one another, so that, sooner or later, it nearly always results in a difference in' characteristics which is sufiicient to produce rupture. It follows therefrom that in practice near the ideal condition of exact similarity, but without reaching the same.

By completely avoiding the glaze, by using the method of the present invention, the risk of rupture which is dependent upon the difference in characteristics of the materials of the body and the glaze, is entirely eliminated. i

Having thus described our invention and 0 in what manner the same is to be performed, we claim as new and desire to secure by Letters Patent the following:

1. A process of producing porcelain articles which comprises the steps of placing an anti-adhesive mixture of refractory and glutinous substances on said articles and submitting said articles with saicTanti-adhesive mixture, in piles, to a temperature at which vitrification takes place.

7 2. A process of producing porcelain articles which comprises the steps of placing an anti adhesive mixture of refractory and glutinous substances on said articles, arranging said articles so that the outside bottom of one article contacts the inside bottom of an adjacent article and submitting the articles, in

)iles to a tem ieratureat which vitrification takes place, whereby the mixture of refractory and glutinous substances does not remain attached to the inside bottom of the articles. i V

3. The process of producing porcelain articles comprising the steps of polishing said articles, placing a mixture of refractory and glutinous materials on said articles, submit ting the articles having the mixture thereon,

in piles, to a temperature at which vitrifica I mixture thereon, in piles to a temperature I at which vitrification takes place,.and finally polishing said article.

" GIOVANNI FUSCHI.

MAURIZIO KORACH. 

